Methods for fabricating group III nitride compound semiconductors and group III nitride compound semiconductor devices

Abstract

The present invention provides a Group III nitride compound semiconductor with suppressed generation of threading dislocations. A GaN layer 31 is subjected to etching, so as to form an island-like structure having a shape of, for example, dot, strip, or grid, thereby providing a trench / mesa structure, and a mask 4 is formed at the bottom of the trench such that the upper surface of the mask 4 is positioned below the top surface of the GaN layer 31. A GaN layer 32 is lateral-epitaxially grown with the top surface 31a of the mesa and sidewalls 31b of the trench serving as nuclei, to thereby bury the trench, and then epitaxial growth is effected in the vertical direction. In the upper region of the GaN layer 32 formed above the mask 4 through lateral epitaxial growth, propagation of threading dislocations contained in the GaN layer is 31 can be prevented.

Description

TECHNICAL FIELD[0002]The present invention relates to a method for fabricating Group III nitride compound semiconductors. More particularly, the present invention relates to a method for fabricating Group III nitride compound semiconductors employing epitaxial lateral overgrowth (ELO). The Group III nitride compound semiconductors are generally represented by AlxGayIn1-x-yN (wherein 0≦x≦1, 0≦y≦1, and 0≦x+y≦1), and examples thereof include binary semiconductors such as AlN, GaN, and InN; ternary semiconductors such as AlxGa1-xN, AlxIn1-xN, and GaxIn1-xN (wherein 0<x<1); and quaternary semiconductors such as AlxGayIn1-x-yN (wherein 0<x<1, 0<y<1, and 0<x+y<1). In the present specification, unless otherwise specified, “Group III nitride compound semiconductors” encompass Group III nitride compound semiconductors which are doped with an impurity so as to assume p-type or n-type conductivity.BACKGROUND ART[0003]Group III nitride compound semiconductor are direct-tr...

AI Technical Summary

Benefits of technology

[0005]The aforementioned dislocations will next be described with reference to a schematic representation shown in FIG. 23. FIG. 23 shows a substrate 91, a buffer layer 92 formed thereon, and a Group III nitride compound semiconductor layer 93 further formed thereon. Conventionally, the substrate 91 is formed of sapphire or a similar substance and the buffer layer 92 is formed of aluminum nitride (AlN) or a similar substance. The buffer layer 92 formed of aluminum nitride (AlN) is provided so as to relax misfit between the sapphire substrate 91 and the Group III nitride compound semiconductor layer 93. However, generation of dislocations is not reduced to zero. Threading dislocations 901 propagate upward (in a vertical direction with respect to the substrate surface) from dislocation initiating points 900, penetrating the buffer layer 92 and the Group III nitride compound semiconductor layer 93. When a semiconductor element is fabricated by laminating various types of Group III nitride compound semiconductors of interest on the Group III nitride compound semiconductor layer 93, threading dislocations further propagate upward, through the semiconductor element, from dislocation arrival points 902 on the surface of the Group III nitride compound semiconductor layer 93. Thus, according to conventional techniques, problematic propagation of dislocations cannot be prevented during formation of Group III nitride compound semiconductor layers.

[0044]By forming a light-emitting element atop a lateral-epitaxially grown portion of the Group III nitride compound semiconductor layer produced through the above process, a light-emitting element endowed with improved service life and an improved LD threshold value can be provided (claim 15).

Problems solved by technology

However, when a Group III nitride compound semiconductor is formed on a sapphire substrate, misfit-induced dislocations occur due to difference between the lattice constant of sapphire and that of the semiconductor, resulting in poor device characteristics.

Misfit-induced dislocations are threading dislocations which penetrate semiconductor layers in a longitudinal direction (i.e., in a direction vertical to the surface of the substrate), and Group III nitride compound semiconductors are accompanied by the problem that dislocations in amounts of approximately 109 cm−2 propagate therethrough.

When such a semiconductor is incorporated in, for example, a light-emitting device, the device poses problems of unsatisfactory device characteristics in terms of threshold current of an LD, service life of an LED or LD, etc.

On the other hand, when a Group III nitride compound semiconductor is incorporated in any of other types of semiconductor devices, because electrons are scattered due to defects in the Group III nitride compound semiconductor, the semiconductor device comes to have low mobility.

These problems are not solved even when another type of substrate is employed.

Thus, according to conventional techniques, problematic propagation of dislocations cannot be prevented during formation of Group III nitride compound semiconductor layers.

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